Edit: the following has been paraphrased because the original poster is upset. I'm taking a trip this week and I'm worried about sending my Kindle through the X-ray machine. The last time I did that, my ereader did not survive. True, it was a netronix clone but there was no reason to end its short, pitiful, useless, disappointing life with a cracked screen.
Any advice? I know that the screen could have cracked for any number of reasons, but once bitten twice shy. I don't want to be trapped on a week long trip with nothing to read. Mind you though, that netronix thing was of exceptionally poor quality.
Unfortunately, this ebook reader owner had the bad luck to encounter a rare type of airport X-ray machine. It's not intended to be physically destructive, but it does have a design quirk or 2. You see, it sounds like this ereader went through an experimental scanner. I've heard of this once or twice, and apparently the manufacturer managed to integrate some of the aspects of the Magic Mirror Gate from The Neverending Story.
As you probably know, the MM Gate shows you your true self. Brave men find themselves to be cowards. Heros are sometimes revealed as villains. But the Gate always shows the truth, which is why it's so damaging.
In this case the truth was not a good idea, because the ereader was forced to face the fact that it was a substandard product. It clearly couldn't accept the truth about itself and it committed suicide by breaking its own screen. It's tragic, I know, but we can't all live a lie forever.
Here's the truth about screen breakage. It can happen for unexplained reasons, no matter how careful you are. One screen broke on me after I knew for certain that I had been careful to protect the ereader.
Joking aside, if you're worried about the screen breaking in the scanner then remove the ereader from your bag and put it in one of the bins. Send the bin through the scanner on its own. That should protect it from impact damage.